This invention relates to self-diagnosis type protecting devices for computer-controlled apparatuses such as copying machines, and more particularly to a self-diagnosis type protecting device which prevents the trouble that, when a specified output terminal (or a specified component) is solely started and stopped irrespective of other input or output terminals, the specified output terminal overruns to damage other output or input terminals.
In maintenance and inspection or repair of a copying machine or the like, a method has been employed in which components (or output terminals such as motors, relays and lamps) are operated individually irrespective of their normal cooperative operation so that they are subjected to self-diagnosis according to an inspection program which is stored in advance. A conventional self-diagnosis method, which is applied to a copying machine, will be briefly described with reference to FIG. 1.
FIG. 1 is a block diagram of a copying machine which is controlled by a computer. In FIG. 1, reference numeral 1 designates a CPU (central processing unit); 2, a ROM (read-only memory); 3, a RAM (random access memory); 4, an input port; and 5, an output port.
Further in FIG. 1, reference numeral 6 designates a common buss connecting the CPU 1, the ROM 2, the RAM 3, the input port 4 and the output port to one another; 10, a copying machine body which is connected through the input port 4 and the output port 5 to a computer section (consisting of the CPU 1, the ROM 2, the RAM 3, etc.); and 10A, the front panel of the copying machine body 10.
In self-diagnosis, the operating mode of the copying machine is changed from a copying mode to a self-diagnosis mode by operation switches (not shown) provided on the front panel or in another suitable location.
Thereupon, the keys and switches on the front panel 10A display the self-diagnosis mode, specify parts to be inspected (output terminals such as motors, relays, lamps, etc.), start or stop the parts thus specified, and display the states of these parts. In general, a ten-key array is used to specify the parts to be inspected, a copy start key and a copy stop key are used to start and stop the designated parts, respectively, and various display lamps and number-of-sheet display units are employed to display the states of these parts.
In association with this, a self-diagnosis program which has been stored in the ROM 2 is called out and executed by operating the keys on the front panel.
Heretofore, in the self-diagnosis of the copying machine as described above, only a specified output terminal is individually started and stopped under the condition that the operations of other associated output terminals or input terminals are stopped or made ineffective. This method suffers from the following drawbacks.
(1) When a lamp, for instance, is specified so as to be turned on, it is necessary to simultaneously start the cooling fan. If, in this case, the cooling fan is not started, the lamp and components around the lamp may be damaged.
(2) When either of the fractional magnification optical system driving motor or the sheet feeding tray driving motor, for instance, are specified and started, it is necessary to receive signals from limit switches adapted to limit the movement of the motor within an allowable value, to thereby control the driving motor. Otherwise, the fractional magnification optical system or the sheet feeding tray will overrun their respective limit positions to damage either themselves or other adjacent components.
In order to eliminate the above-described difficulties, it is necessary for the operator, at the same time as an output terminal is specified in self-diagnosis, to specify an input terminal and/or an output terminal which relates to the output terminal thus specified. This is undoubtedly troublesome for the operator.